Fix quagga peering by working around the NAT

Quagga peering doesn't seem to work over the NATted openstack external
network. To work around this, directly patch the quagga instance to the
external network and give it a fixed IP in that network. Then, all the
peering traffic goes over that patched interface.

Change-Id: I8d9d8fef4e86839c821f83e564d5c49cc15e43ae
JIRA: SDNVPN-114
Signed-off-by: Romanos Skiadas <rski@intracom-telecom.com>